#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <pwd.h>

int main(int argc, char **argv){
	struct passwd *pwdline;
	if(argc < 2){
		fprintf(stderr,"Usage...\n");
		exit(1);
	}

	pwdline = getpwuid(atoi(argv[1]));
	puts(pwdline->pw_name);
	exit(0);


}
